Bug 66010 – REGRESSION(r92670-r92744): WebKit crashes when opening Gmail

• Status: RESOLVED
• Resolution: FIXED
• Component: WebKit Misc.

[Ryosuke Niwa]

Reproduction steps:
1. Go to www.google.com/mail/
Crash!

This appears to be JSC issue because it doesn't reproduce on Chromium.

[Oliver Hunt]

Can we get a crashtrace and platform?

[Ryosuke Niwa]

Stack trace:

Thread 0 Crashed:  Dispatch queue: com.apple.main-thread
0   com.apple.JavaScriptCore      	0x00000001007daec5 JSC::DFG::JITCompiler::jumpFromSpeculativeToNonSpeculative(JSC::DFG::SpeculationCheck const&, JSC::DFG::EntryLocation const&, JSC::DFG::SpeculationRecovery*, JSC::DFG::NodeToRegisterMap&, JSC::DFG::NodeToRegisterMap&) + 5909
1   com.apple.JavaScriptCore      	0x00000001007dc25a JSC::DFG::JITCompiler::linkSpeculationChecks(JSC::DFG::SpeculativeJIT&, JSC::DFG::NonSpeculativeJIT&) + 282
2   com.apple.JavaScriptCore      	0x00000001007dcc87 JSC::DFG::JITCompiler::compileBody() + 2359
3   com.apple.JavaScriptCore      	0x00000001007ddf04 JSC::DFG::JITCompiler::compileFunction(JSC::JITCode&, JSC::MacroAssemblerCodePtr&) + 788
4   com.apple.JavaScriptCore      	0x0000000100817241 JSC::FunctionExecutable::compileForCallInternal(JSC::ExecState*, JSC::ScopeChainNode*, JSC::ExecState*) + 2193
5   com.apple.JavaScriptCore      	0x00000001008324db JSC::Interpreter::prepareForRepeatCall(JSC::FunctionExecutable*, JSC::ExecState*, JSC::JSFunction*, int, JSC::ScopeChainNode*) + 523
6   com.apple.JavaScriptCore      	0x000000010078a1af JSC::arrayProtoFuncForEach(JSC::ExecState*) + 2831
7   ???                           	0x00003b3019e011e8 0 + 65077778584040
8   com.apple.JavaScriptCore      	0x0000000100831245 JSC::Interpreter::execute(JSC::ProgramExecutable*, JSC::ExecState*, JSC::ScopeChainNode*, JSC::JSObject*) + 1573
9   ???                           	0x0000000106f357a0 0 + 4411578272

[Geoffrey Garen]

<rdar://problem/9931900>

[Ryosuke Niwa]

(In reply to comment #1)
> Can we get a crashtrace and platform?

Snow Leopard on MacPro.

[Filip Pizlo]

Created attachment 103545 [details]
the patch

[Geoffrey Garen]

*** Bug 66011 has been marked as a duplicate of this bug. ***

[WebKit Review Bot]

Comment on attachment 103545 [details]
the patch

Clearing flags on attachment: 103545

Committed r92804: <http://trac.webkit.org/changeset/92804>

[WebKit Review Bot]

All reviewed patches have been landed.  Closing bug.

[Alexey Proskuryakov]

*** Bug 66115 has been marked as a duplicate of this bug. ***

[Adam Roben (:aroben)]

Is it not possible to write an automated regression test for this?

[Geoffrey Garen]

Seems like it should be possible. If possible, all checkins should come with a regression test.

[Filip Pizlo]

(In reply to comment #10)
> Is it not possible to write an automated regression test for this?

Sorry for not noting this in the ChangeLog, but there is no obvious automated regression test.  The bug arises out of misuse of a hidden "this" argument to constructor calls.  This is a synthetic notion introduced in our bytecode and our JITs - it is not exposed in the JavaScript language.

As well, the bug only happens when three different register allocators in the system (the bytecompiler's virtual register allocator, the DFG parser's virtual register allocator, and the DFG back-end's physical register allocator) all make exactly the "wrong" decision based on the input.  A test that would cause a failure just before this fix landed would be unlikely to continue to cause failures if even slight changes in register allocation were made subsequently.